Apparatus for feeding solid fuels to furnaces



March 1965 M. v. u. PIETERSE APPARATUS FOR FEED :s SOLID FUELS TO FURNACES Filed July 11, 1962 United States Patent 3,174,445 APPARATUS FOR FEEDING SOLID FUELS T0 FURNACES Marius van Uye Pieterse, Haanplein 24, The Hague, Netherlands Filed July 11, 1962, Ser. No. 209,113 Claims priority, application Great Britain, July 20, 1961,

26,268/ 61 4 Claims. (Cl. 110-104) This invention relates to apparatus for feeding solid fuel to furnaces and is an improvement in or modification of the invention disclosed in United States Patent No. 3,006,- 293, issued October 31, 1961.

In practice it has become apparent that in the provision of a long conduit for feeding the fuel, which conduit is especially suitable for mounting within a boiler in such a way that the conduit passes, at least for a great part of its length, through the steamand/0r water-space of the boiler to the furnace, the coal stream participates insufiiciently in the gyratory movement of the air current owing to the high velocity of the fall, so that the coals to a large extent fall from the conduitin a more or less straight path in consequence of the greater kinetic energy acquired by the coal particles.

Thus a homogeneous mixing of the coals does not take place and even distribution over the bed of the furnace fails to occur.

The object of the present invention is to obviate or mitigate the above disadvantages of the use of long fuel conduits.

According to the present invention, apparatus for feeding solid fuel to a furnace comprises a fuel conduit extending through at least a large portion of the boiler and discharging on to the bed of the furnace, and means such as an air-supply tube adapted to direct compressed air substantially tangentially into the conduit at the inlet end thereof so as to impart a gyratory motion to the falling fuel, the compressed airiat said inlet end directly pressing the descending fuel against the inner wall of the conduit for the greater part of said wall, Where the velocity of the compressed air is the highest, and said velocity being reduced to zero in the centre of the conduit.

As there are different velocities of the tangential air in the vertical conduit, the remainder of the coal stream more or less remote from the wall of said conduit passes downwardly, as this velocity gradually decreases from said wall to the centre of the conduit and reduces to zero.

In consequence the coal particles at the centre of the conduit have less tendency to be thrown outwards so that an even distribution of the coals over the bed of the furnace is obtained, the grate surface lying vertically under the conical-shaped end of the conduit.

It will be clear that by regulating the compressed air which is chiefly active on the descending and rotating coal stream, the distribution of the fuel over the bed of the furnace is correspondingly controlled.

Preferably, in order to ensure that the centreof the conduit also is filled with coal particles, a valve is mounted within a supply tube connected tangentially to the inlet end of the conduit for the coals, said valve having a central spindle which is rotatable intermittently so that on the valve being given successive impulses the compressed air and the coals are blown at intervals against the inner wall of the conduit, and the centre of the conduit is thereby provided with coal particles which pass to the bottom in free fall.

Preferably also the conduit has means to retard or brake the velocity of the fall of the coal stream and said means are located between the inlet end of the conduit and a peripheral series of tangential air nozzles discharging into the conduit at the bottom thereof, the arrangement being such that while there is a long conduit and in consequence a high velocity of fall, an even distribution of the coals over the bed of the furnace is obtained. Thus, the conduit includes, almost immediately above the bottom air nozzles, a frusto-conical part converging downwards to retard or brake the Velocity of the fall of the coal stream, and/or one or more tangential air nozzles are disposed at intervals below the inlet end of the conduit and discharge into the conduit, said intermediate nozzle or nozzles being sloped upwards and inwards to direct air flow against the direction of flow of the coals and so retard the velocity of fall of the coal stream.

The velocity of the compressed air passing through the intermediate nozzles maintains'the gyratory motion of the air column which is started by the compressed air in the tube connected tangentially to the inlet end or top of the conduit.

Owing to the characteristics as above recited, in the conduit there occurs a homogeneous mixing of the coals which rotate rapidly around the axis of the conduit so that the coals passing through the mouth of the conduit are evenly distributed over the bed of the furnace assisted by the high velocity ofthe fall arising from the long length of the conduit.

Other characteristics and advantages of the apparatus according to the invention will now be describedand explained below with reference to the accompanying drawing in which is illustrated by way of example an embodiment of the invention;

FIG. 1 shows the old method in which the coals fall through the conduit without compressed air being used so that inadequate spreading of the coals over the grate is obtained;

FIG. 2 shows a longitudinal section of a boiler provided with improved spreading means;

FIG. 3 shows the manner in which the compressed air tangentially introduced into the conduit has a maximum velocity at the inner wall of the conduit and is reduced to zero at the axis of the conduit;

FIG. 4 is a section along the line IVIV of FIG. 2 and shows the manner in which the coal particles, or most of them, are guided by the compressed air tangentially introduced into the conduit, and are carried along the inner wall of the conduit;

.FIG. 5 is a section of an embodiment which is a somewhat modified version of FIG. 2, the boiler and the furnace being omitted for clearness;

2 FIG. 6 is a cross-section along the line VI-VI of FIG.

; and

FIG. 7 is a cross-section along the line VIIVlI of 7 Pro.- 2.

Referring to the drawings:

A feed-screw conveyor 4 (not shown in FIG. 2) is arranged in a tube 3 which conveyor supplies the coals to an upright cylindrical fuel conduit 2 connected to the screw tube 3. 1

According to FIG. 1, the coals fall freely downwards without being subjected to ,the action of compressed air tangentially introduced into the conduit 2, and consequently an even distribution of the coals over the bed of the furnace is not obtained.

Therefore, according to FIGS. 2 to 4 a tube 14 is mounted tangentially at the top (or inlet) end of the vertical conduit 2 for guiding compressed air the purpose of which will be explained hereinafter.

The conduit 2 which has its outlet above the centre of the grate in the double walled furnace 1, is connected at the inlet end to the screw tube 3, in which, as abovementioned, is arranged a screw conveyor 4 of which the shaft 6 is driven e.g. by an electro motor (not shown).

Around the conduit 2, between the inlet and outlet ends, is arranged concentrically a cylindrical housing or {3 tube 7 which is connected to a compressed air generator or tank (not shown).

Said compressed air is injected-as FIG. 7 shows tangentially into the conduit 2 by means of guides 8 and channels 9 arranged in the wall of the conduit 2.

The lower end of the conduit 2 is of conical shape as indicated at 12 and the inner face of the cone is provided with ribs 13, the purpose of this arrangement being as described in British Patent No. 816,745, issued July 15, 1959. The improvement in this arrangement lies chiefly in that, as application of a long conduit 2 which passes, at least for a great part of its length through the steamand/or water-space of the boiler and far into the furnace, results inthe coal stream participating insufficiently in the gyratory movement of the air current owing to the high velocity of the fall, a tube 14 is mounted tangentially at the top (or inlet) end of the vertical conduit 2 for injecting compressed air so that the compressed air causes directly at said top end a rotation of the coals about the axis of the conduit 2, and thus gyration of the fuel along the conduits inner wall where the velocity of the compressed air is the highest, the velocity reducing to zero at the axis of the conduit 2.

In order to ensure that the centre also of the conduit is filled with coal particles, for even distribution of the coals over the bed of the furnace, within the tube 14 is mounted a throttle valve 15 which has a central spindle 16 rotatable e.g. by a source of power 17, to which valve impulses can be given intermittently by a disc provided with two cams (not illustrated); the purpose of the intermittent operation is explained hereinbefore.

In order to brake or to retard the high velocity of the fall of the coals, means are provided in the conduit 2, which means are located between the top or inlet end of said conduit 2 and the bottom air nozzles 9, and consist of (a) one or more tangential air nozzles 19 discharging into said conduit and sloped upwards and inwards to direct airflow against the direction of flow of the coal particles, and/ or (b) a'frusto-conical part 18 (FIG. 5) converging downwards and embodied in the conduit 2 immediately above the bottom nozzles.

Between the conduit 2 and the tube 7 surrounding the conduit are mounted vertical supply pipes 20 for feeding compressed air to the intermediate nozzles 19, which pipes 20 are closed at their lower ends.

The supply of compressed air to the pipes 20 is effected via a connection 21 which is in communication with a compressed-air generator or tank.

In the space between the wall of the conduit 2 and the wall of the concentric tube 7, compressed air is guided, via a connection 22, along the exterior of the vertical supply pipes 20 to the bottom air nozzles.

The connections 21 and 22 may be supplied from one and the same source of compressed air, and may be individually regulatable.

The concentric tube 7 is, in order to avoid overheating, surrounded by a cylindrical jacket 23 which is in communication at the top with the water-space of the boiler and at the bottom communicates with the water-space through water-tubes 24.

The tube 7 and its conical end 25 form a unit with the conical mouth 12 while the vertical conduit 2 with the bushing 9 which is provided with the air-nozzles 9 and tightly engages the conduit 2 are detachably mounted, by means of e.g. asbestos packing, on the parts 12 and 25, the arrangement being such that the conduit 2 together with the supply pipes 21 and the top piece 26 for the tube 7, following uncoupling of the flanges 27, 28 and 29, are removable from the boiler as an unit for servicing, cleaning or renewal of one or other part of said unit.

The fire-door of the boiler is denoted by 30, and the grate by 31, while at the top of the furnace is mounted a smoke-box 32' which communicates with the chimney (not shown).

It will be understood that the present invention is not restricted to the embodiment as described and illustrated, which may be varied without departing from the scope of the invention.

Thus, it is possible instead of providing a. series of intermediate air nozzles, to provide a single air nozzle extending in a longitudinal direction.

What I claim is:

1. Apparatus for feeding solid fuel to a furnace housing, said apparatus comprising, in combination,

a substantially vertical fuel conduit adapted to extend downwardly into said furnace housing and having an upper portion, an inlet opening in said upper portion adapted to be positioned outside said furnace, housing, a lower portion, and an outlet opening in said lower portion adapted to be positioned in said furnace housing;

fuel input means for feeding solid fuel into the inlet opening of said fuel conduit;

braking means positioned in operative proximity with said fuel conduit intermediate the inlet and outlet openings thereof for reducing the velocity of fuel in said fuel conduit, said braking means comprising spaced groups of peripherally positioned spaced tangential air channels opening into said fuel conduit and means for supplying air through said air channels; and

directing means positioned in said upper portion of said fuel conduit ahead of said braking means for imparting a gyratory motion to fuel in the said fuel conduit so that a substantial portion of fuel in said fuel conduit is thrown against the inside walls of said fuel conduit during its travel through the said fuel conduit and the fuel discharged through the outlet opening of said fuel conduit is adapted to be substantially uniformly distributed in said furnace housing, said directing means comprising tangential air channel means opening into said fuel conduit and means for supplying air through said air channel means.

2. Apparatus for feeding solid fuel to a furnace housing, said apparatus comprising, in combination,

a substantially vertical fuel conduit adapted to extend downwardly into said furnace housing and having an upper portion, an inlet opening in said upper portion adapted to be positioned outside said furnace housing, a lower portion, and an outlet opening in said lower portion adapted to be positioned in said furnace housing;

fuel input means for feeding solid fuel into the inlet opening of said fuel conduit;

braking means positioned in operative proximity with said fuel conduit intermediate the inlet and outlet openings thereof for reducing the velocity of fuel in said fuel conduit, said braking means comprising spaced groups of peripherally positioned upward and inward directed spaced tangential air channels opening into said fuel conduit and means for supplying air through said air channels whereby the air supplied through said air channels is directed against the direction of movement of said fuel in said fuel conduit and reduces the velocity of the said fuel; and

directing means positioned in said upper portion of said fuel conduit ahead of said braking means for imparting gyra-tory motion to fuel in said fuel conduit so that a substantial portion of fuel in said fuel conduit is thrown against the inside walls of said fuel conduit during its travel through the said fuel conduit and the fuel discharged through the outlet opening of said fuel conduit is adapted to be substantially uniformly distributed in said furnace housing, said directing means comprising tangential air channel means opening into said fuel conduit and means for supplying air through said air channel means.

3. Apparatus for feeding solid fuel to a furnace housing,

said apparatus comprising, in combination,

a substantially vertical fuel conduit adapted to extend downwardly into said furnace housing and having an upper portion, an inlet opening in said upper portion adapted to be positioned outside said furnace housing, a lower portion, and an outlet opening in said lower portion adapted to be positioned in said furnace housing;

fuel input means for feeding solid fuel into the inlet opening of said fuel conduit;

an air conduit around said fuel oonduit extending from directing means positioned in said upper portion of said said fuel conduit ahead of said tangential air channels for imparting a gyratory motion to fuel in the said fuel conduit so that a substantial portion of fuel in said fuel conduit is thrown against the inside walls of said fuel conduit during its travel through the said fuel conduit and the fuel discharged through the outlet opening of said fuel conduit is adapted to be substantially uniformly distributed in said furnace housing, said directing means comprising tangential air channel means opening into said fuel conduit and means for supplying air through said air channel means.

Apparatus for feeding solid fuel to a furnace housing, apparatus comprising, in combination,

substantially vertical fuel conduit adapted to extend downwardly into said furnace housing and having an upper portion, an inlet opening in said upper portion adapted to be positioned outside said furnace housing, a lower portion and an outlet opening in said lower portion adapted to be positioned in said furnace housing;

fuel input means for feeding solid fuel into the inlet opening of said fuel conduit;

said fuel conduit intermediate the inlet and outlet openings thereof for reducing the velocity of fuel in said fuel conduit, said braking means comprising a plurality of spaced groups of peripherally positioned upward and inward directed spaced tangential air channels opening into said fuel conduit and means for supplying air to said air channels whereby the air supplied to said air channels is directed against the direction of movement of said fuel in said fuel conduit and reduces the velocity of the said fuel, and an air conduit around said fuel conduit extending from said upper portion of said fuel conduit in the direction of said lower portion thereof and a plurality of peripherally positioned spaced nozzles opening from said air conduit into said fuel conduit and means for supplying air through said air conduit and said nozzles, whereby the air is directed against the fuel in said fuel conduit so as to reduce the downward velocity of said fuel; and

directing means positioned in said upper portion of said fuel conduit ahead of said braking means for imparting a gyratory motion to fuel in the said fuel conduit so that a substantial portion of fuel in said fuel conduit is thrown against the inside walls of said fuel oonduit during its travel through the said fuel conduit and the fuel discharged through the outlet opening of said fuel conduit is adapted to be substantially uniformly distributed in said furnace, said directing means comprising tangential air channel means opening into said fuel conduit and means for supplying air through said air channel means.

References Cited in the file of this patent UNITED STATES PATENTS 1,542,834 Peehles et al June 23, 1925 2,601,690 Hague June 24, 1952 2,654,831 Mo'sshart Oct. 6, 1953 3,006,293 Pieterse Oct. 31, 1961 FOREIGN PATENTS 704,901 Great Britain Mar. 3, 1954 816,745 Great Britain July 15, 1959 

1. APPARATUS FOR FEEDING SOLID FUEL TO A FURNACE HOUSING, SAID APPARATUS COMPRISING, IN COMBINATION, A SUBSTANTIALLY VERTICAL FUEL CONDUIT ADAPTED TO EXTEND DOWNWARDLY INTO SAID FRAME HOUSING AND HAVING AN UPPER PORTION, AN INLET OPENING IN SAID UPPER PORTION ADAPTED TO BE POSITIONED OUTSIDE SAID FURNACE, HOUSING, A LOWER PORTION, AND AN OUTLET OPENING IN SAID LOWER PORTION ADAPTED TO BE POSITIONED IN SAID FURNACE HOUSING; FUEL INPUT MEANS FOR FEEDING SOLID FUEL INTO THE INLET OPENING OF SAID FUEL CONDUIT; BRAKING MEANS POSITIONED IN OPERATIVE PROXIMITY WITH SAID FUEL CONDUIT INTERMEDIATE THE INLET AND OUTLET OPENINGS THEREOF FOR REDUCING THE VELOCITY OF FUEL IN SAID FUEL CONDUIT, SAID BRAKING MEANS COMPRISING SPACED GROUPS OF PERIPHERALLY POSITIONED SPACED TAN- 